Rolling high helix pinions

ABSTRACT

Rolling pinions having a high helix angle using a helical roll with the teeth of the roll inclined at a helix angle such that axial thrust on the pinion due to inclination of the teeth is substantially counterbalanced by axial thrust due to crossed axes sliding.

1451 Dec. 12, 1972 8/1962 Bregi et a1. 4/1963Newman................................72/104 [S4] ROLLING HIGH HELIXPINIONS a [72] Inventor: David W. Daniel, Birmingham,

Mich.

[731 Assignee: Lear Sieglel', Inc., Santa Monica,

Primary Examiner-Lowell A. Larson Attorney-Whittemor'e, l-lulbert &Belknap Calif. T I Nov. 19,1970 ABS RACT Rolling pinions having a highhelix angle using a helical roll with the teeth of the roll inclined ata helix [221 Filed:

[21] Appl.No.:90,946

- I angle such that axial thrust on the pinion due to .72/102,72/101,29/1 59'1 inclination of the teeth is substantially countertocrossed axes sliding.

[52] US. Cl. [51] Int. Cl. ....B2lh 5/00 alanced by axial thrust due[58]- Field of Search..........72/80, 101, 102, 105, 106,

References Cited UNITED STATES PATENTS 7 Claims, 1 Drawing Figure 6/1941Draderetal.

ROLLING HIGH HELIX PINIONS BRIEFSUMMARY OF THE INVENTION When rollingpinions having a relatively high helix angle, where the pinion is drivenin rotation by a gearlike rolling die, the forces applied to the teethof the pinion as they are formed develop an axial component of force ofvery considerable magnitude. Up to the present time efforts to rollpinions of this type have generally been in an arrangement in which theaxes of the pinion and gear-like rolling die are parallel.

According to the, present invention the magnitude of the helix angle ofthe teeth of the rolling die are caused to differ from the magnitude ofthe helix angle of the teeth to be rolled on the pinion by a fewdegrees. The result of this is'that to produce teethof the requiredhelix angle on the pinion, the axes of the pinion and die must becrossed by an angle determined by the difference in magnitude of thehelix angles.

As a result of the crossed axes relationship between the die and gear,there is a relative sliding movement between the surfaces of the teethon the die and the surfaces of the pinion teeth as they are formed,which is longitudinal of the teeth or generally parallel to the axis ofthe pinion. This slidingmotion is referred to as crossed axes slide andis of course to be distinguished between the sliding action taking placebetween conventional involute gears at parallel axes which is referredto as involute slide. Involute slide varies from zero at the operatingpitch line on the surfaces of the gear teeth to maxima adjacent the rootand crest of the teeth, and the direction of specific'sliding on thepinion tooth surfaces reverses at the pitch line and the specificdirection (whether toward or away from the pitch line) depends uponwhether the tooth surface is the leading or following surface of thetooth.

Accordingly, by appropriately selecting the helix angle of the dieteeth, the rolling operation may produce forces resulting from thecrossed axes slide, as defined heretofore, which balance orsubstantially balance the forces due to the rolling action on theinclined teeth.

BRIEF DESCRIPTION OF THE DRAWING The FIGURE is a diagrammatic view inwhich the crossed axes angle is exaggerated forclarity, showing arolling die in mesh with a pinion.

DETAILED DESCRIPTION In rolling gears or pinions, and particularly in anoperation in which a pinion is rolled from a solid cylindricalblank,present practice is to drive the gear-like rolling die positively inrotation and to drive the work blank as it is formed into a gear by therotation of the die. The operation is carried out by providing a diehaving identically formed teeth around its periphery, and the formationof the teeth on the blank as the blank and die are rolled together, isaccomplished by providing a relative depth feed of the die into theblank along the line joining the axes of the blank and die.

Referring now to the drawing there is illustrated a die having inclinedteeth 12. This die is shown as in mesh with a finished work piece orpinion 14 having helically inclined teeth 16. The illustrationpresupposes that the die has been moved radially into the blank to adepth sufficient to produce the teeth 16. Further, it may be assumedthat the die is being positively driven in the direction of rotationindicated by the arrow superimposed thereon, in which case of course thepinion is being rotated in the direction suggested by the arrowsuperimposed on the pinion. I

Where the teeth of the pinion have a relatively great helix angle as forexample substantially above 45, forces are developed in driving thepinion in rotation which are essentially perpendicular to the teeth andwhich therefore have a component of force directed axially of thepinion. Such component of force is indicated by the arrow 18 and it willbe observed that this force is to the left as seen in the FIGURE.

It is further to be understood that this force, due to the drivingrelationship between the die and pinion and the direction of inclinationof the teeth, is substantially independent of any crossed axesrelationship between the pinion and die. This force or a forcesubstantially equal to this force would be present if the pinion wererolled by a die whose teeth had equal but opposite helix angle so thatthe axes of the die and pinion were parallel.

However, when the axes of the pinion and die are crossed as indicated inthe FIGURE, it will be appreciated that there is a relative slidingmotion introduced between the teeth of the die and the teeth as they areformed and finally shaped on the pinion. This forming the teeth at thetop of the pinion have a component of motion parallel to the axis of thepinion 14 which extend to the right as viewed in the FIGURE. Thiscomponent of motion is designated by the arrow 20 in the FIGURE.

Thus, by a proper selection of helix angle of the die teeth, it ispossible to develop a component of force as a result of crossed axesslide which is parallel to the axis of the pinion and which is equal andopposite to the component of force parallel to the axis of the piniondeveloped by the driving forces acting between the teeth of the die andpinion.

It has been found that when these forces are substantially balanced,deflection of machine parts is substantially eliminated and a smoothrolling operation results.

When the die is designed to operate with its axis parallel to the axisof the pinion or work blank, the teeth produced on the pinion are of ahelix angle equal in magnitude and opposite in hand to the teeth on thedie. In order to provide a balancing component of axial force due tocrossed axes slide, the helix angle of the teeth of the die will beincreased in magnitude by a small angle, normally between A" and 4. Whenthis pinion is then set at a crossed axes so as to produce the requiredhelix angle of teeth on the pinion, the actual forces due to toothinclination and crossed axes slide are opposed and may be balanced orsubstantially balanced by selection of the appropriate helix angle. Theexact helix angle giving the best results may require trial and error.However, this trial may be carried out by using a single approximatelycorrect helix angle die at slightly different crossed axes. While thiswill produce corresponding slight differences in helix angle on theteeth of the gear, the best helix angle setting can be determined afterwhich further dies may be produced having teeth of the helix angle tooperate at the predetermined crossed axes setting to produce teeth ofprecisely the required helix angle on the pinion.

By way of example, a pinion having 50 left hand helical teeth may beproduced by a die having 52 right hand helical teeth at a crossed axessetting of 2.

In the foregoing description of the principles involved, reference hasbeen made to the FIGURE which shows a pinion produced or finished byrolling engagement with a single gear-like die. It is to be understoodthat the invention may be practice in a finish rolling operation inwhich a gear has been produced by conventional methods such for exampleas hobbing, shaper cutting, or the like, and in which the rollingoperation as described herein is to displace a relatively small amountof material to bring the gear to exact required final dimensions and toimprove the surface and tooth form characteristics.

Alternatively of course, the method may be carried out by sinking therolling die into a cylindrical blank so as to form the teeth simply bythe rolling operation.

While the FIGURE illustrates a single die in mesh with the pinion, it isto be understood that the invention may be carried out by using a singledie, a pair of opposed dies, or even an arrangement of three or moredies spaced angularly about the periphery of the pinion or blank. Wherethe operation is rolling teeth on a cylindrical blank, or rolling a gearfrom the solid, it will normally be accomplished by a plurality of diesso as to balance radial forces on the pinion.

It will of course further be understood that where two or more dies areemployed simultaneously on a pinion or blank, the axial thrust producedon the teeth of the pinion by both or all of the dies must beconsidered, and that in addition, the axial thrust of both or all of thedies resulting from the crossed axes sliding action producing componentsof force acting axially of the pinion, must be considered.

The foregoing may be expressed as requiring the algebraic sum of all ofthe components of forces between the pinion and the die or dies inengagement therewith acting axially of the pinion is substantially zero.

What I claim as my invention is:

l. The method of rolling the teeth of pinions of high helix angle toproduce teeth thereon of final finished form by a displacement of metalswhich comprises providing a gear-like rolling die having smooth surfacedhelical teeth in which the helix angle is of slightly greater magnitudeand opposite hand from the teeth to be formed on the pinion and selectedin relation to the helix angle of the pinion teeth to cause the axialcomponent of force on the pinion during rotation due to pressure betweenthe tooth surfaces of the die and pinion to substantially balance theaxial component of force on the pinion due to the friction duringrotation between the tooth surfaces due to the crossed axes relationshipof the die and pinion, positioning the die with its axis crossed withrespect to the axis of the pinion at an angle determined by thedifference in magnitude of the helix angle of the die teeth and theteeth to be formed on the pinion, driving the die in rotation, and

relatiyel moving the die and tplinion along a line perp endicu at to anintersecting err axes with sufficient force to sink the die teeth intothe material of the pinion to displace the material to form the pinionteeth to final form.

2. The method as defined in claim 1 in which the teeth formed on thepinion have a helix angle in excess of 45.

3. The method as defined in claim 1 in which the crossed axes angle isbetween 30' and 4.

4. The method as defined in claim 1 in which the teeth formed on thepinion have a helix angle in excess of 45, and in which the crossed axesangle is between 30' and 4.

5. The method as defined in claim 1 which comprises employing aplurality of dies simultaneously in circumferentially spaced relationabout the periphery of the pinions.

6. The method as defined in claim 5 in which the helix angles of thedies are selected such that the algebraic sum of axial components ofthrust on the pinion as a result of forces applied to the teeth of thepinion in effecting rotation thereof and the forces developed by thecrossed axes sliding action between the teeth of the dies and the teethof the pinion is substantially zero.

7. The method as defined in claim 1 in which the pinion at the start ofthe rolling operation is in the form of a substantially cylindricalblank and in which pinion teeth are initially rolled up out of thematerial of the blank and finally finished rolled to final form.

1. The method of rolling the teeth of pinions of high helix angle toproduce teeth thereon of final finished form by a displacement of metalswhich comprises providing a gear-like rolling die having smooth surfacedhelical teeth in which the helix angle is of slightly greater magnitudeand opposite hand from the teeth to be formed on the pinion and selectedin relation to the helix angle of the pinion teeth to cause the axialcomponent of force on the pinion during rotation due to pressure betweenthe tooth surfaces of the die and pinion to substantially balance theaxial component of force on the pinion due to the friction duringrotation between the tooth surfaces due to the crossed axes relationshipof the die and pinion, positioning the die with its axis crossed withrespect to the axis of the pinion at an angle determined by thedifference in magnitude of the helix angle of the die teeth and theteeth to be formed on the pinion, driving the die in rotation, andrelatively moving the die and pinion along a line perpendicular to andintersecting their axes with sufficient force to sink the die teeth intothe material of the pinion to displace the material to form the pinionteeth to final form.
 2. The method as defined in claim 1 in which theteeth formed on the pinion have a helix angle in excess of 45*.
 3. Themethod as defined in claim 1 in which the crossed axes angle is between30'' and 4*.
 4. The method as defined in claim 1 in which the teethformed on the pinion have a helix angle in excess of 45*, and in whichthe crossed axes angle is between 30'' and 4*.
 5. The method as definedin claim 1 which comprises employing a plurality of dies simultaneouslyin circumferentially spaced relation about the periphery of the pinions.6. The method as defined in claim 5 in which the helix angles of thedies are selected such that the algebraic sum of axial components ofthrust on the pinion as a result of forces applied to the teeth of thepinion in effecting rotation thereof and the forces developed by thecrossed axes sliding action between the teeth of the dies and the teethof the pinion is substantially zero.
 7. The method as defined in claim 1in whiCh the pinion at the start of the rolling operation is in the formof a substantially cylindrical blank and in which pinion teeth areinitially rolled up out of the material of the blank and finallyfinished rolled to final form.